<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
				var i=prompt("请输入成绩：")
					function  sandaiyi(i)
					{if(i>=90){
						return false;
					}else if(i>=80
					){
						return ture;
						
				}
					return false;
					}
					alert(sandaiyi(str));
		</script>
	</body>
</html>
